Preparation of Bi-2212/YBCO heterostructure and their interfacial characters

YBa₂Cu₃O_7-x (YBCO) thin films were prepared on LaAlO₃ (LAO) substrates by a sol–gel method, and the epitaxial growth of Bi-2212 thin films on YBCO thin films was investigated. Both YBCO and Bi₂Sr₂Ca₁Cu₂O_8+δ (Bi-2212) bilayer films exhibit good biaxial texture and superconducting properties. Afterward, a cross-shaped Bi-2212/YBCO heterostructure was fabricated, and its interfacial atomic arrangement and I-V characteristics were analyzed. Atomic-resolution STEM images obtained from a spherical-aberration-corrected transmission electron microscope show that two superconducting films exhibit a layered structure and the atoms inside the films are artfully arranged. Moreover, the order of the seven atomic layers between Bi-2212 and YBCO layers with a thickness of about 1.32 nm is misarranged. Among them, the Y-O layer of YBCO and the Sr-O layer of Bi-2212 share a CuO₂ layer. The I-V curves of Bi-2212/YBCO bilayer films show that the seven misarranged atomic layers at Bi-2212/YBCO interface acts as a barrier layer, which means that a Josephson junction can be fabricated using this interface characters.